Interleukin-22, or “IL-22” hereafter, is an IL-10 related cytokine, that had previously been referred to as “TIF” or “IL-TIF” for “interleukin-10 related, T cell inducible factor.” See U.S. Pat. Nos. 6,359,117; 6,331,613 and 6,274,710, as well as Dumoutier, et al., J. Immunol 164:1814-1819 (2000), all of which are incorporated by reference in their entirety. The molecule belongs to a family of cytokines with limited homology to IL-10, including IL-10, IL-22, mda-7/IL-24, IL-19, IL-20 and AK155/IL-26. See Moore, et al., Annu. Rev. Immunol 19:683-765 (2001); Dumoutier, et al., Eur. Cytokine Netw 13(1):5-15 (2002). The cytokine shows 22% amino acid identity with IL-10. Functionally, IL-22 activities which have been identified include upregulation of acute-phase reactants in liver and hepatoma cells (Dumoutier, et al., supra,) as well as induction of pancreatitis-associated protein (PAP 1), in pancreatic acinar cells (Aggarwal, et al., J. Interferon Cytokine Res. 21:1047-1053 (2001)), suggesting a role for the cytokine in inflammatory processes. In addition, IL-22 has been shown to induce STAT activation in several cell lines, including mesangial cells, lung and intestinal epithelial cells, melanomas, and hepatomas. See Dumoutier, et al., supra; Dumoutier, et al., Proc. Natl. Acad. Sci USA 97:10144-10149 (2000); also see patent application Ser. No. 09/626,617, filed Jul. 27, 2000, incorporated by reference which referred to “TIF” as IL-21; however, the molecule has been renamed as IL-22.
The IL-22 molecule binds at cell surfaces to a receptor complex composed of two chains, which belong to the Class II cytokine receptor family, i.e., IL-22R and IL-10Rβ. See, e.g., Dumoutier, et al., Proc. Natl. Acad. Sci USA 97:10144-10149 (2000); Xie, et al., J. Biol. Chem 275:31335-31339 (2000); Kotenko, et al., J. Biol. Chem. 276:2725-2732 (2000); also see U.S. patent application Ser. No. 09/915,735, filed Jul. 26, 2001, and incorporated by reference. This family of receptors includes receptors for type I and type II interferons, such as IFNAR1, IFNAR2, IFNGR1 and IFNGR2; IL-10Rα, IL-22R/CRF2-9, IL-10Rβ/CRF2-4, IL-20Rα/CRF2-8, IL-20Rβ/CRF2-11, and tissue factor. See Kotenko, et al., Oncogene 19:2557-2565 (2000); Blumberg, et al., Cell 104:9-19 (2001); Kotenko, Cytokine Growth Factor Rev 217:1-18 (2002), all of which are incorporated by reference.
With the exception of IL-10R per se, signaling through the receptors for IL-10 related cytokines has not been investigated very well. The binding of IL-10 to its receptor complex (IL-10Rα and IL-10Rβ), induces activation of JAK-1, and Tyk-2 tyrosine kinases. Experiments by Finbloom et al., J. Immunol. 153:1079-1090(1995), showed that JAK-1 associates with IL-10Rα, and Tyk-2 copreciptates with IL-10Rβ. See Kotenko, et al., EMBOJ 16:5894-5903 (1997), regarding Tyk-2. Activation of the two kinases, in turn, leads to phosphorylation of STAT1, 3 and 5. See Finbloom, et al., J. Immunol 153:1079-1080 (1995); Wehinger, et al., FEBS Lett 394:365-370 (1996). In addition, IL-10 is known to activate P13 kinase, and p70S6 kinase (Crawley, et al., J. Biol. Chem 271:16357-16362 (1996)), but not the MAP kinase pathway. Indeed, Sato, et al., J. Immunol 162:3865-3872 (1999), and Geng, et al., Proc. Natl. Acad Sci USA 91:8602-8606 (1994), show that IL-10 inhibits this pathway in monocytes and dendritic cells.
The inventors have investigated the mechanism of action involved in the binding of IL-22 to its receptor, and have discovered a pathway of activation not reported previously. Since IL-22 and IL-10 share one receptor subunit, i.e., IL-10Rβ, and the functional receptor complex involves IL-22R for IL-22, and IL-10Rα for IL-10, it was believed, initially, that the signalling pathways would be nearly identical; however, this has proven to not be the case. It has now been shown that IL-22 induces phosphorylation of JAK-1 and Tyk-2, but not JAK-2. It has also been shown that JAK-1 is absolutely required for IL-22 signaling to occur. While IL-10 also activates JAK-1 and Tyk-2, and both induce phosphorylation of the same STATs, it has now been shown that IL-22 induces activation of ERK, JNK and p38 pathways, which IL-10 does not. In addition, it has been shown that IL-22 induces serine phosphorylation of STAT3, which IL-10 does not.
These, and other features of the invention will be evidenced in the disclosure which follows.